Use [`funcall` or `apply`](https://www.gnu.org/software/emacs/manual/html_node/elisp/Calling-Functions.html#Calling-Functions):

```lang-el
(setq wrapped-copy (symbol-function 'emacs-version))
(fset 'fn (lambda () (funcall wrapped-copy)))

(fn)
"GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 2.24.32, cairo version 1.16.0)
 of 2020-06-15"
```

Although, in general, I would use an [advice](https://www.gnu.org/software/emacs/manual/html_node/elisp/Advising-Functions.html#Advising-Functions) for wrapping a function.